(1) Field of the Invention
The present invention relates to an apparatus for evaluating quality of a granular object which analyzes the quality of the granular object such as an agricultural product, a food product and an industrial material.
(2) Description of the Related Art
For such granular objects as grains, pellets, chip-capacitors, and tablets, a quality evaluation apparatus is used to determine foreign objects or defective objects, or extent of such objects, to calculate the mixing ratio of such objects, and to determine the quality ranking of products or to set standards for quality control.
An example of the quality evaluation apparatus of grains has been disclosed in Japanese Patent Application Kokai Publication No. Hei 9-292344. The disclosed apparatus calculates the number of grains based on the quality related factors such as normal grains, immature grains, damaged or colored grains. This quality evaluation apparatus is arranged such that a disk provided at the peripheral edge thereof with a plurality of sample receiving holes is rotated, and the sample grains in the sample receiving holes are subjected, one grain at a time, to the irradiation of light, and thus the reflection light or the transmission light is received. A detection section for detecting a grain is provided above the disk, and is equipped with two light receiving elements for dividing the amount of the vertical reflection light into a long wavelength component and a short wavelength component and receiving the light for respective wavelengths, a vertical transmission light receiving element provided below the disk for receiving the vertical transmission light, a light receiving element for detecting a crack in a rice grain by receiving the slanted transmission light. The evaluation data are calculated from the amounts of light received by these four light receiving elements, and the quality of the grains, one by one, is determined based on the above evaluation data and the predetermined evaluation algorithm.
Also, there is another quality evaluation apparatus in which the image data are obtained by taking the images of a plurality of sample rice grains, the contour of individual rice grains is determined from the image data, and the quality of the rice grain is determined from the contour and the color of the image of the rice grain determined by the contour as well as the predetermined evaluation algorithm.
However, in the quality evaluation apparatus disclosed in the Japanese Patent Application Kokai Publication No. Hei 9-292344, although the grain detection section is composed of the two light receiving elements for receiving the vertical reflection light obtained by irradiating the rice grain from the light source, one light receiving element for receiving vertical transmission light, and one light receiving element for detecting a crack in a rice grain by receiving the slanted transmission light, the arrangement is such that the optical information is not obtained from both the front side and the back side of the rice grain. For example, the optical information which evaluates the quality of the rice grain, such as green dead-kernel rice grains or immature rice grains, only by the spectrum ratio of the vertical reflection light, the evaluation is made only from the data obtained from the front side of the rice grain (that is, only from the reflection light obtained from above the rice grain) and the data from the back side of the rice grain (that is, the amount of reflection light obtained from below the rice grain) has not been taken into account. Although it is rare, there are situations wherein no proper evaluation can be carried out because of an abnormal hue that appears only at the back side of the rice grain or because of the influence of the shade of the apparatus onto the rice grain.
Further, in the quality evaluation apparatus disclosed in the above publication, although the grain detection section, particularly the light receiving element for detecting a crack of a granular object is equipped with one crack detection light receiving element for receiving slanted transmission light irradiated from a slanted direction of the rice grain, no sufficient optical information is obtained at the time of the detection of the crack. The crack in the grain refers to a grain in which the crack occurs in the albumen thereof. The degrees of the cracked grains are divided into the five stages, namely, (1) a grain in which one crosswise crack runs all through, (2) a grain in which two cracks which do not run across completely are present on one crosswise surface and which, when observed from the other surface, are in two crosswise cracks, (3) a grain in which three cracks not running all through are present on one crosswise surface, (4) a grain in which any lengthwise cracks are present, and (5) a grain in which a tortoiseshell type crack is present. In this prior art example, since the optical information is taken-in by only one crack detection light receiving element, there was a possibility to overlook the crack on the other surface, or the lengthwise crack.
Also, even when the quality evaluation apparatus is with the configuration of the latter, that is, one in which the image data are obtained by taking the images of a plurality of sample rice grains, the operation in which the optical information are obtained from one side of the rice grain has failed to maintain a high precision of the quality evaluation. With this apparatus, it is impossible to achieve an accurate determination of cracks in the grains.
An object of the present invention is to overcome the above problems and to provide a quality evaluation method and an apparatus in which the data from both the front and back sides of the granular object are analyzed thereby enhancing the precision of the results of the quality analysis, especially the precision in the crack detection.
According to one aspect of the invention, there is provided a method for evaluating the quality of granular objects, the method comprising the steps of:
irradiating the granular objects selectively from a front side and a back side of the granular objects;
taking a reflection light image and a transmission light image from the front and back sides of each of the irradiated granular objects;
obtaining optical information of each of the granular objects by image-processing the reflection light image and the transmission light image;
obtaining shape information of the granular objects based on the optical information;
determining the quality of each of the granular objects based on the optical information and the shape information, the quality of granular objects including such quality as complete and incomplete granular objects;
counting the numbers of the granular objects per quality and obtaining ratios per quality of the granular objects against the total number of the granular objects;
preparing sample images of the granular objects per quality by processing the optical information; and
simultaneously displaying or printing the respective numbers of the granular objects per quality, the ratios per quality of the granular objects and the sample images of the granular objects.
The sample images per quality are displayed or printed after having been arranged in a predetermined format such as a matrix form according to the respective numbers of the granular objects per quality calculated based on the ratios and the total number of the granular objects.
The method may further comprise a step of establishing a granular object quality evaluation formula based on analysis in which the quality of the granular object whose quality is known is used as objective variables and the optical information and the shape information obtained from the granular object whose quality is known are used as explanatory variables, wherein a quality for the granular objects whose quality is unknown is evaluated based on the granular object quality evaluation formula and the optical information and the shape information obtained go therefrom.
The optical information includes hue, saturation and intensity of the granular objects.
The shape information including length, width and area of the granular objects is obtained from the intensity within the optical information.
According to another aspect of the invention, there is also provided an apparatus for evaluating the quality of granular objects, the apparatus comprising:
granular object holding means formed of a material which transmits light incident thereon;
light source means for irradiating light on front and back sides of each of the granular objects held by the granular object holding means;
background means for establishing references to reflection light or transmission light from or through each of the granular objects;
image taking means for obtaining image signals of reflection light images and transmission light images from both the front and back sides of each of the granular objects, and slanted light images of one of the front and back sides of each of the granular objects;
image processing means for converting the plurality of image signals obtained by the image taking means into optical information relating to the quality of the granular objects, and converting the optical information into shape information;
arithmetic and control means for determining the quality of the granular objects per quality based on the optical information and the shape information which are obtained by the image processing means; and
indicating means for displaying or printing simultaneously the results of quality evaluation obtained by the arithmetic and control means and the shape information obtained by the image processing means.
One of the light source means may comprise four separate light sources which irradiate the granular objects diagonally from four directions, the four light sources being turned on or off simultaneously or independently from each other, a plurality of the slanted light images being obtained when the four light sources are sequentially turned on.
The arithmetic and control means stores sample images of the granular objects per quality and calculates the numbers of the granular objects per quality based on the ratios of the granular objects per quality and the total number of the granular objects, arranges the order of the stored sample images according to the results of the above calculation, and outputs the results of the quality evaluation of the granular objects and the arranged sample images to the indicating means.
The arithmetic and control means stores a granular object evaluation formula obtained by analysis in which the quality of the granular object whose quality is known is used as objective variables and the optical information and the shape information obtained from the granular object whose quality is known are used as explanatory variables, and a quality of the granular object whose quality is unknown is obtained by applying the optical information and the shape information obtained from the image processing means to the granular object quality evaluation formula.
The light source means is of a circular or a ring-like shape.